Cellular or radio telephony systems utilize numerous microwave devices, such as waveguides, bandpass filters, couplers, combiners or diplexers, attenuators and resonators. Such a device exhibits selected responses to specific input signals, and these responses may be realized either by selecting and using a device having the desired response or by changing the characteristics of a single device until the desired response is achieved. Changing the characteristics of a resonant RF cavity, such as a bandpass filter, involves altering the electrical and/or magnetic characteristics thereof. For example, both bandpass Q and insertion loss depend to some extent on the electrical length L of a resonant cavity, and bandpass Q depends on the characteristics of dielectric substances (usually air) present in the cavity. Changing the characteristics of the cavity, therefore, may include altering L of the cavity by selective movement of an electrically conductive plate therein or selectively inserting into, or removing from, the cavity a non-air dielectric member.
There are several cellular telephone protocols or standards, and these include, on the one hand, Advanced Mobile Phone Service (“AMPS”) and Time Division Multiple Access (“TDMA”), and, on the other hand, Enhanced Data Rate for GSM Evolution (“EDGE”). The former protocols utilize a 30 kHz bandwidth, while the latter utilizes a 200 kHz bandwidth. It may be desirable to include as subscribers to cellular telephone service in a single system of interest both subscribers using one protocol, such as AMPS/TDMA, and those using another protocol, like EDGE, in one or more or all of the cells of the subject cellular telephone system. In this event, the subject system must be capable of simultaneously operating according to the plural protocols, AMPS/TDMA or EDGE. As new subscribers using one or the other protocol join the subject system, and as present subscribers roam from cell to cell and to the subject system from other systems the ratio of subscribers using one protocol to those using other protocols change, causing the cells to change and fluctuate with time.
Changes and fluctuations may require that the ratio of AMPS/TDMA capacity to EDGE capacity (or vice versa) of the transceivers in the cells of the system be periodically adjusted. The foregoing presents a problem, inasmuch as the base stations of cellular telephone systems are usually large in number and are often remotely located from the business or service offices of the system's service provider. Moreover, these base stations are usually unmanned.
From the foregoing, as set forth more fully below, there is a need to imbue multi-protocol cellular telephone systems with the ability to adjust the capacities of base station transceivers to simultaneously handle varying demands for communication services based on the variant protocols.